Epithelial malignancies represent the vast majority of human cancers. A common feature of carcinomas is the invasion of neoplastic cells through the basement membrane that sets the stage for local and distant metastases, the major cause of morbidity and mortality in patients. The critical tumor-stroma interactions occurring at the basement membrane during early human tumor progression have yet to be fully characterized. This proposal focuses on the role of the 1 and 4 integrin subunits as well as the integrin associated focal adhesion kinase (FAK) in mediating early epidermal tumor progression. First, we plan to extend recent findings that 1 and 4 integrin and their multiple integrin partners are key components of an extracellular matrix-centric gene expression network in human epidermal tumor progression. Targeting of 1 integrin modestly attenuated neoplastic progression in an epidermal tumor xenograft model(1). We have designed experiments using blocking antibodies and RNA interference to target 1 and 4 integrin in a 3-D human epidermal tissue model to further characterize their role in neoplastic basement membrane invasion. The possibility of a cooperative role of 1 and 4 integrins in early epidermal tumor progression will be investigated. These studies are designed to characterize the role of integrins in early epidermal tumorigenesis. Second, we will characterize the role of FAK activation in the human epidermal neoplasia model. Increased expression of FAK has been reported in human squamous cell carcinomas(2). Initial experiments will determine the effect of integrin blockade on FAK phosphorylation as a surrogate of FAK activity during epidermal tumorigenesis. Subsequently, we will test if expression of FAK can overcome the effect of integrin blockade on epidermal tumor progression. Finally, we plan to characterize the functional significance of a FAK kinase domain mutation that we recently identified in a human cutaneous squamous cell carcinoma. The mutant FAK will be expressed in the inducible epidermal neoplasia model to determine its effect on neoplastic basement membrane invasion. These studies are designed to define the role of FAK in mediating epidermal neoplastic progression. At the end of the proposed funding period, we hope to have characterized the role of the 1 and 4 integrin subunits as well as the downstream signaling kinase FAK during early epidermal tumor progression. The results may identify therapeutic strategies to treat epithelial cancers.